In a precast reinforced concrete bridge unit having a headwall, for example, as disclosed in U.S. Pat. No. 4,993,872 which issued to the assignee of the present invention, it is known to cast the headwall as an integral part of an end bridge unit when the bridge unit is being cast, for example, as shown in the '872 Patent. It is also known to precast the headwall separately with a bottom arcuate abutment or collar which extends continuously across the arcuate top wall of the bridge unit. The collar is secured to the top wall of the bridge unit by bolts or threaded rods which extend into the top wall and are threaded into concrete anchors embedded within the top wall. The continuous arcuate collar provides for attaching the vertical headwall to the bridge unit at the construction site.
It is desirable for the headwall to be precast separately from the precast bridge unit for significantly reducing the weight of the precast bridge unit and to facilitate shipping the precast bridge unit along a roadway or highway with a semi-truck and low bed trailer vehicle. The separate precast headwall units also facilitate handling and shipping of the headwall units on a semi-truck and trailer vehicle. After all of the bridge units are positioned at the construction site with the aid of a crane, the headwall units are then positioned with the crane and attached to the opposite end bridge units.